As a rotation ring having an inner ring with a first rolling element travel groove, an outer ring with a second rolling element travel groove facing the first rolling element travel groove, and a plurality of rolling elements interposed between the first rolling element travel groove and the second rolling element travel groove, for instance, a bearing device in which an object is mounted on at least one of the inner ring and the outer ring is widely known.
A bearing device for a steering column in which three or more resin balls and three or more steel balls having smaller diameters than that of the resin balls are disposed between an outer ring and an inner ring in a circumferential direction is disclosed in Patent Literature 1 shown below. According to this configuration, a large load in the event of collision is received by the steel balls and a variation in a radial gap of a bearing is absorbed by minute deformation of the resin balls, and thus rattling or the like of a steering shaft can be prevented.